Ignition system



Feb..13, 194a, v. EIMOCARTY 2,189,913

IGNITION SYSTEM Filed Aug. 31, 1938 INVENTOR' M6 BY *7 W ATTORNEXLPatented Feb. 13, 1940 PATENT OFFICE IGNITION SYSTEM Verle E. McCarty,Anderson, Ind., assignor to General Motors Corporation, Detroit, Mich. acorporation of Delaware Application August 31, 1938, Serial No. 227,65!

comma.

This invention relates to method and apparatus for reducing pitting ofignition timer contact points and more particularly to the methods andapparatuses disclosed in the copending application of Herman L.Hartzell, Serial No.'

276,396 filed May 29, 1939, which is a continuation in part of abandonedapplication 8. N. 227,775 filed August 31, 1938.

The Hartzell application, discloses that during ignition timer contactseparation two kinds of pitting may occur. When the contact separationis .0003' or less, there is a transfer of material from the positivecontact to the negative contact due to electronic bombardment of thepositive contact, thereby causing the surface of the positive contact tobe heated and material thereof to passtherefrom as a metallic vaporwhich condenses on the negative contact. This is called transfer to thenegative. The second kind of pitting is due to transfer of material fromthe negative contact to the positive contact. This occurs at a contactseparation greater than .0003" and is due to ionic bombardment of thenegative contact causing the material thereof to pass as a metallicvapor to the positive contact where it condenses. This is calledtransfer to the positive. In order that transfer of'material from thepositive contact may occur some time during contact separation exceeding.0003", the voltage applied across the contacts should be at least 340volts. According to the Hartzell application this voltage may be reachedby combining, at the time of secondary dis-- charge, the primary inducedvoltage with a transient voltage derived from a high frequencyoscillation accompanying secondary discharge in order to produce an areat the timer contacts which will transfer material from the negativetimer contact to the positive timer contact.

wThis transient voltage is derived by means of a capacity couplingbetween the insulated terminal of the timer and the secondary circuit.By a proper selection of the value of this capacity, the arc at thecontacts produced by the combined induced. primary voltage and voltagederived from the high frequency oscillation will be such that thetransfer of. material to the positive contact will compensate for thetransfer of \material to the negative contact. In this way so flatcontact operation is obtained.

When providing ignition for the modern automobile equipped with a radioreceiver, it is necessary to place in the circuit between the ignitioncoil secondary terminal and the center terminal as of the ignitiondistributor cap, a radio interference suppressor in the formof aresistor or choke. While this resistor or choke suppresses objectionableinterference by the ignition system with the radio receiver, it alsosuppresses the effect of the high frequency transient upon 5 the timercontacts and, therefore, materially decreases transfer to the positivecontact. The radio suppressor is useful in an ignition system which isnaturally disposed to transfer more material to the positive contactthan to the 10 negative. In such systems the radio interferencesuppressor would tend to correct transfer to the positive. But in mostignition systems used on relative high speed automobile engines, thetendency is to transfer to the negative 15 rather than to the positive.The Hartzell application discloses how to correct transfer to thenegative in an ignition system in which it is necessary to use a radiointerference suppressor. This is accomplished by the capacity-coupling20 of one or more of the spark plug leads tothe insulated timerterminal. The number of capacity-couplings used depends on the amount ofcorrection required to compensate for transfer of the material to thenegative contact. 25

I have discovered that, with some installa tlons of ignition equipmentfor passenger automobiles, it is safe to take advantage of all of thehigh frequency transients which occur and, therefore, to usecapacity-couplings between the timer contacts and all of the spark plugleads. Instead of providing a separate coupling with each lead, Iprovide one coupling between the insulated timer terminal and the centerterminal of the distributor cap. In case( a radio inter- .15 ferencesuppressor is used in the\ connection between the ignition coilsecondary terminal and the center terminal of the-distributor cap,Iconnect the capacity in between the suppressor and the center terminal.i so In order to facilitate making the connection between the centerterminal of the distributor cap and with the radio suppressor and withthe capacity-coupling as well as the connection between the radiosuppressor and the ignition coil 45 secondary terminal, I provide aunitary structhe condenser which provides the capacity-coupling betweenthe insulated terminal or the timer and a point between theradiosuppressor and the center terminal of the distributor cap. Themounting/of this unit upon the ignition timer provides" the connectionbetween the capacity-cOupling, condenser and the insulated terminal ofthe ignition timer.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawing wherein a preferred embodiment of the present invention isclearly shown.

In the drawing:

Figure 1 is a wiring diagram illustrating an ignition system embodyingthe present invention:

Figure 2 is a fragmentary perspective view of an ignition timer equippedwith the unitary structure which provides a cable connector between theignition coil secondary terminal and the center terminal of thedistributor cap, which houses the radio interference suppressor andwhich provides the condenser for effecting a capacity-coupling betweenthe insulated terminal of the ignition timer and some point between theradio interference suppressor and the center terminal of the distributorcap;

Figure 3 is a top plan view of the unit shown in Figure 2; and

Figure 4 is a sectional view taken on the line 4-4 of Figure 3.

Referring to Figure l, the ignition system comprises a battery 20grounded at 2| and connected with the primary winding 22 of ignitioncoil 24 having a secondary winding 23 connected with the primary andwith the insulated terminal 25 of the ignition timer 26 having contacts21 and 28. These contacts are shunted by the usual ignition condenser29.

Numeral 30 designates the ignition distributor cap having distributorposts or terminals 3 I, each connected by wire 82 with a spark plug 33rounded at 2|. Sparking impulses are distributed to the post 3] by anengine distributor rotor (not shown) connected in well known manner withthe center terminal 34 of the ignition distributor cap 30. Theconnections between thecap terminal 34 and the high tension terminal 23aof the coil 24 comprises a wire 35, a resistance 35 providing the radiointerference sup- Dressor and a wire 31.

In order to obtain ilat contact operation in the manner which has beenpointed out, a condenser 40 or capacity-coupling is provided between theinsulated or non-grounded terminal 25 of the timer 25 and a pointbetween the radio inter ference suppressor 25 and the center terminal 34of the distributor cap 30. In order to facilitate making connectionsbetween the units 36 and 40 and other parts of the apparatus, I providea unitary structure-50, shown in Figures 2, 3 and 4, which is, supportedby the ignition timer 28 in the manner shown in Figure 2.

The unit 50 comprises a sleeve ll made of Bakelite or other moldableinsulating material. Sleeve 50 carries a tubular metallic insert 52 anda thimble-like metallic insert 58. Within the insert 52 is located anon-conducting tube 54 made of material having a high dielectricstrength. As a material for this tube isolantite has been foundsatisfactory. The isolantite tube 54 receives a carbon resistanceelement 56 which provides the resistor shown at 38 in Figure 1.Resistance, is urged by-a spring 51 against the insert a. said springI'lfbeing confined by a metal disk 58 which has a press flt within theinsert 52. As indicated diagrammatically in Figure 1, the insert 52provides a terminal socket for receiving a metallic plug, thimble orferrule fixed to one end of the cable 35 which, as shown structurely inFigure 2 as well as diagrammatically in Figure 1, makes connectionbetween the insert 52 and the center terminal 34 of the distributor cap30. Insert 52 is electrically connected with the resistor 56 through thedisk 58 and the spring 51. The insert 53 provides a terminal socketwhich receives a ferrule on the end of wire 3'! formaking connectionbetween the resistor and the high tension terminal 23a of the ignitioncoil 24.

The manner in which the unit 50 provides the condenser 40 will now bedescribed. The two plates of the condenser 40 are provided,respectively, by the tubular metal sleeve 52 within the insulatingsleeve 5| and an outer tubular sleeve which is provided by the bracket6| by which the unit 50 is mounted. The bracket 8! is formed of sheetmetal so as to provide the tubular part 60 which surrounds the sleeve 5iand to provide the end portions 62 and 53 which are riveted together bya single rivet 84 to provide a mounting pad 65. The pad has two holes 68and 81 either of which are large enough to receive the usual terminalscrew or stud with which the ignition timer terminal 25 is provided. Theunit 50 is therefore mounted upon the screw 25a of the insulatedterminal 25 and is secured in position by a nut. Hence, the condenser 40is provided by concentric cylindrical tubes 52 and 80 with a dielectricbetween them provided by the insulating sleeve 51.

From the foregoing, it is apparent that the present invention relates toan ignition system which provides for flat contact operation by the useof a capacity coupling between the nongrounded or insulated terminal ofthe ignition timer and some point in the connection between the hightension terminal of the ignition coil and the center terminal of thedistributor can. This connection is such that the coupling condenser iseffective regardless of the use of a radio interference suppressor. Inits preferred form, the present invention embraces a unitary structurewhich can be attached to the conventional form of ignitiontimer-distributor and which provides the capacity-coupling, the radiointerference suppressor and the facilities for conveniently connectingthe unit with other units of the system.

While the embodiment of the present invention as herein disclosed,constitutes a preferred form, it is to be understood that other formsmight be adopted, all coming within the scope of the claims whichfollow.

What is claimed is as follows:

1. An ignition system for internal combustionengines comprising, incombination, a current source, an ignition coil having a primary windingand a. secondary winding, a timer having contacts for controllingconnection of the current source to the ignition coil primary, aninsulated terminal provided by the timer and connected with one of thetimer contacts, a wire connecting said timer insulated terminal with theignition coil primary winding, a timer condenser connected with thetimer contact which is connected with said insulated timer terminal, adistributor including a center terminal for distributing sparkingimpulses generated in the secondary winding to the spark plugs of theengine, and a 75 condenser having one electrodedirectly attached to theinsulated timer terminal and its other electrode connected electricallywith the center terminal of the distributor for. the purpose ofsupplementin'g the primary-induced voltage, at the time of secondarydischarge, with a transient voltage derived from a high frequencyoscillation which accompanies the discharge, of the second-.

ary circuit across the spark gap, whereby to produce an are at the timercontacts which will producetransfer of -material to the-positive timercontact to compensate for transfer of material to the negative contact.

2. An ignition system for internal combustion engines comprising, incombination, a current source, an ignition coil having a primary windingand a secondary winding, a timer having contacts for controllingconnection of the current source to the ignition coil primary,anlnsulated terminal provided by the timer and connected with one of thetimer contacts, a wire connecting said. timer insulated terminal withthe ignition coil primary winding, a timer condenser connected with thetimer contact which is connected with said insulated timer terminal, adistributor including a center terminal for distributing sparkingimpulses generated in the secondary winding to the spark plugs of theengine, and a condenser having concentric tubular electrodes, the outerone being mounted upon the insulated timer terminal and the inner oneproviding a wireconnector-socket, a wire connected with the centerterminal of the distributor and provided with a connector-plug receivedby said socket, said last named condenser operating for the purpose ofsupplementing the primary induced voltage, at the time of secondarydischarge, with a transient voltage derived from a highfrequencyoscillation which accompanies the discharge of the secondarycircuitacross the spark gap, whereby to produce an are at the timer contactswhich will produce transfer of material to the positive timer contact tocompensate for transfer of material to.

the negative contact.

3. An ignition system for internal combustion engines comprising, incombination, a current source, an ignition coil having a primary windingand a secondary winding, a timer having contacts for controllingconnection of the current source to the ignition coil primary, aninsulated terminal provided by the timer and connected with one of thetimer contacts, a wire connect ing said timer insulated terminal withthe ignition coil primary winding, a timer condenser connected with thetimer contact which is connected with said insulated timer terminal, adistributor including a center terminal for distributing sparkingimpulses generated in the secondary winding to the spark plugs oftheengine, and a condenser having concentric tubular electrodes separatedby a non-conducting sleeve, the outerl electrode being mounted upon theinsulated timer terminal and the inner one providing awireconnector-socket, a wire connected with the centerterrninal of thedistributor and 'provided with a connector-plug received by said socket,a second wire-connector-socket provided bysaidsleeve', a wire connectedwith the ignition coil secondary winding and provided with aconnector-plug re-' ceived by said second socket, means for connectingthe second socket with said inner electrode,

age, at the time of secondary discharge, with a transient voltagederived from a frequency oscillation which accompanies the discharge ofthe secondary circuit across the spark gap, whereby to produce an are atthe timer contacts which will produce transfer of material to thepositive timer contact to compensate for transfer of material to thenegative contact.

4. An ignition system for internal combustion engines comprising, incombination, a current source, an ignition coil having a primarywindingand a secondary winding, a timer having contacts for controllingconnection of the current source to the ignition coil primary, aninsulated terminal provided by the timer and connected with one of thetimer contacts, a wire connecting said timer insulated terminal with theignition coil primary winding, a timer condenser connected with thetimer contact which is connected with said insulated timer terminal, adistributor including a center terminal for distributing aconnector-plug received by said socket, a second wire-connector socketprovided by said sleeve, a wire connected with the ignition coilsecondary winding and provided with a connector-plug received by saidsecond socket, means including a vradio-interference-suppressor-resistance housed within said sleeve forelectrically connecting the second socket with said inner electrode,said last named condenser operating for the purpose of supplementing theprimary induced voltage, at the time of secondary discharge, with atransient voltage derived from a high frequency oscillation whichaccompanies the discharge of the secondary circuit across the spark gap,whereby to produce an are at the timer contacts which will producetransfer of material. to the positive timer contact to compensate fortransfer of material to the negative contact.

5. For use with an internal-combustion-engine ignition system comprisinga current source, an ignition coil having a primary winding and 'asecondary winding, a timer having contacts for controlling connection ofthe current source to the ignition coil primary and having an insulatedterminal connectedwith one of the contacts and a distributor including acenter terminal for distributing sparking impulses generated in thesecondary winding to the spark plugs of the engine, a unitary structureproviding a condenser having electrodes separated by a dielectric body,a mounting bracketprovided by one of the electrodes for attaching thestructure to the insulated timer terminal, and wire connecting deviceselectrically connected with the other electrode for making connectionswith wires leading, respectively, to the center terminal of thedistributor and to the ignition coil secondary winding.

6. For use with an internal-combustion-engine ignition system comprisinga current source, an ignition coil having a primary winding and asecondary winding, a timer having contacts for controlling connection ofthe current source to the ignition coil primary and having an insulatedterminal connected with one of, the contacts and a distributor includinga center terminal for dis-- tributing sparking impulses generated in thesecondary winding to the snark plugs of the engine, a unitary structurepl'OVldlllg a condenser having concentric tubular electrodes separatedby a dielectric sleeve, a mounting bracket provided by the outerelectrode for attaching the structure to the insulated timer terminal, awire-connectorsocket provided by the inner electrode for receiving anattachment plug on a wire connected with the center terminal of thedistributor, and wire attaching means connected with the inner electrodeof the condenser for making connection with the ignition coil secondarywinding.

7. For use with an internal-combustion-engine ignition system comprisinga current source, an ignition coil having a primary winding and asecondary winding, a timer having contacts for controlling connection ofthe current source to the ignition coil primary and having an insulatedterminal connected with one of the contacts and a distributor includinga center terminal for distributing sparking impulses generated in thesecondary winding to the spark plugs of the engine, a

unitary structure providing a condenser having carried by the structureand electrically connected with the other electrode, and wire connectingdevices respectively connected electrically with said other electrodeand said resistance for making connections with wires leading,respectively, to the center terminal of the distributor and to theignition coil secondary winding.

8. For use with an internal-combustion-engine ignition system comprisinga current source, an ignition coil having a primary winding and asecondary winding, a timer having contacts for controlling connection ofthe current source to the ignition coil primary and having an insulatedterminal connected with one of the contacts and a distributor includinga center terminal for distributing sparking impulses generated in thesecondary winding to the spark plugs of the engine, a unitary structureproviding a condenser having concentric tubular electrodes separated bya dielectric sleeve, a mounting bracket provided by the outer electrodefor attaching'the structure to the insulated timer terminal, awire-connectorsocket provided by the inner electrode for receiving anattachment plug on a wire connected with the center terminal of thedistributor, a radiointerference-suppressor-resistance carried by thestructure and electrically connected with the inner electrode, and awire-attaching-socket carried by the sleeve for receiving a plug' on awire connected with the ignition coil secondary winding, saidsecond-mentioned socket being electrically connected with saidresistance.

VERLE E. McCARTY.

